天然碱性长石的高分辨电镜观察     

西门露露  王岩国  马兴加 《矿物学报》1992,(2)

利用高分辨电子显微镜观察了产于河北汉诺坝玄武岩中碱性长石的精细结构。不同取向的高分辨像清楚地显示了钾、钠长石形成的片层状多重紧密连生体以及各种调制结构。钾、钠长石的连生界面一般为(601)晶面。其超微结构特征与在中等冷却速率下钾钠长石中按旋节分解机制产生的熔离结构相符。以(010)面为孪晶界面的多重连生微孪晶构成了平均周期约为8*d_(010)的调制结构。  相似文献   

新疆西天山莫托萨拉热水沉积型铁锰矿床矿物学与地球化学特征     

董志国  张帮禄  石方平  张连昌  高炳宇  张新  彭自栋  王长乐 《岩石学报》2021,37(4):1099-1121

莫托萨拉铁锰矿床位于西天山阿吾拉勒成矿带东端,研究程度相对薄弱,在矿床成因方面存在热水沉积、沉积-热液改造、胶体化学沉积等争论。本文详细研究了莫托萨拉最上层锰矿及其围岩的矿物组成、结构构造和地球化学特征,并综合前人资料对整个铁锰矿床的成因做了进一步探讨。本研究首次在矿区发现了热液长石岩,其主要由钠长石、钾长石以及少量重晶石、霓石、锌铁黄长石等矿物组成,类似于"白烟型"热水沉积岩。莫托萨拉最上层锰矿主要由锰橄榄石、褐锰矿、红硅锰矿、磁锰铁矿以及少量重晶石、方铁锰矿等矿物组成,发育有典型的热水内碎屑结构,指示其沉积于海底热液喷流口附近。该层锰矿的Al/(Al+Fe+Mn)值很低(0～0.02)、Si/Al值较高(7.9～10.9)、Fe/Ti值很高(428～1353),通过UCC标准化后发现明显富集Zn、Ba、Pb等元素,而Co、Ni、Cu等元素未见富集,以上地球化学特征与现代海底热液成因铁锰沉积物一致。在Fe/Ti-Al/(Al+Fe+Mn)、Si O2-Al2O3、10×(Co+Ni+Cu)-Fe-Mn、100×(Zr+Ce+Y)-15×(Cu+Ni)-(Fe+Mn)/4等判别图中,莫托萨拉的锰矿层和铁矿层样品均落在海底热液沉积区。锰矿层和铁矿层的稀土元素经PAAS标准化后具有明显的Ce负异常、Eu正异常和Y正异常,与现代海底热液成因铁锰沉积物的稀土配分模式非常相似。综合分析本次研究的矿物学、岩石学、地球化学特征以及前人资料,本文认为莫托萨拉铁锰矿床为海相热水沉积成因,成矿与同期海底火山的间歇性活动密切相关,海底热液的化学组分、温度高低和活动强弱都具有明显的脉动性。莫托萨拉矿区铁锰共存但各自独立成矿,且铁锰分离程度较高,这在显生宙沉积型锰矿中独具特色。鉴于前人曾报道莫托萨拉铁矿石中存在菌藻类微生物化石,我们推测,该矿床的铁锰分离过程除了受控于沉积环境的氧化还原条件变化外,微生物的选择性氧化沉淀可能也发挥了重要作用,值得开展深入研究。  相似文献   

新疆阿图什彻依布拉克锡多金属矿点地质特征   总被引：2，自引：0，他引：2  

杨富全  邓会娟  夏浩东  马伯永  王立本 《新疆地质》2003,21(4):426-432

南天山是重要的锡锑多金属成矿带，目前已发现几处锡矿床(点)和大量锡化探异常，具有良好的成矿前景．彻依布拉克锡多金属矿点赋存于塔木岩体围岩的夕卡岩中．塔木碱长花岗岩侵入时代为晚二叠世，化学成分具有富Si、富碱，贫Mg、Al的特点，Ga／Al比值大，富轻稀土，具强Eu负异常，具有A型花岗岩的特点．矿体严格受夕卡岩带控制，呈似层状、透镜状，与夕卡岩产状一致，二呈渐变过渡关系，矿体变化较大．矿石类型有：锡铁矿石、金(铜)矿石、锡矿石和锌铜矿石．成矿具有多阶段性，划分为夕卡岩阶段硼酸盐阶段、硫化物阶段和表生阶段，其中硼酸盐阶段是锡成矿的主要阶段．岩浆活动为成矿提供了热源和主要物质来源．  相似文献   

熔融制样X射线荧光光谱法测定钠长石钾长石中多元素   总被引：4，自引：3，他引：4       下载免费PDF全文

应晓浒  曹国洲 《岩矿测试》2003,22(3):221-224

采用熔融制样X射线荧光光谱法测定钠长石和钾长石中的Na2O、MgO、Al2O3、SiO2、P2O5、K2O、CaO、TiO2、Fe203、Rb、Sr、Y、Zr、Ba14个成分的含量，所得结果与化学分析结果相符，各组分测定33次的仪器RSD为0．10％～4．67％。在试验过程中，对功率为1kW和4kW的两种波长色散型X射线荧光光谱仪的灵敏度和检出限进行了比较，并对仪器的精密度和长期稳定性进行了考察。  相似文献   

Crustal uplift in the southern Superior Province, Canada, revealed by paleomagnetism     

Henry C. Halls  Baoxing Zhang 《Tectonophysics》2003,362(1-4):123-136

A change in the polarity of magnetization with depth in the 2.45 Ga Matachewan dyke swarm is used to document vertical crustal movements that occurred at 1.9–2.3 Ga along the Kapuskasing Structural Zone, a 500-km-long fault zone that transects the Archean Superior Province of Canada. At shallow crustal levels dykes have a primary magnetization dominantly of one polarity, but at greater depths (20 km down) a polarity change occurs associated with the growth of exsolved magnetite in feldspar due to slow crustal cooling after cessation of Matachewan igneous activity. Regions of the dyke swarm with one dominant polarity are separated from those with opposite polarity by major faults. Using this polarity distribution and associated variations in the intensity of feldspar clouding and hydrous alteration, maps of the southern Superior Province are produced that display regional crustal tilting on which are superimposed more local fault-bounded blocks associated with the Kapuskasing zone. Some of these blocks have been recognized for the first time as a result of this study.The paleomagnetic work has also shown that the Matachewan swarm is regionally distorted both within and north of the Kapuskasing zone, and originally had a more radial disposition. This widespread distortion suggests that the lower crust was still relatively ductile at the time of deformation, perhaps due to high heat flow associated with the waning stages of the Matachewan mantle plume beneath.  相似文献   

Thermodynamic modeling of post-entrapment crystallization in igneous phases     

Victor C. Kress  Mark S. Ghiorso 《Journal of Volcanology and Geothermal Research》2004,137(4):247-260

Inclusions of quenched silicate liquid in igneous phenocryst phases represent important windows into the pre-eruption chemistry of volcanic rocks. Melt inclusions are subject to a variety of potential modifications after entrapment, which obscure the connection between final inclusion composition, and entrapment conditions. We concentrate on the effects of post-entrapment crystallization (PEC) in the cooling inclusion. PEC is neither an isobaric nor an isochoric process. Pressure decreases between 2 and 27 bars per degree of cooling, depending on the chemistry of melt and host and on the degree of PEC. In the equilibrium case, between about 50% and 65% of this pressure effect is due to thermal expansivity of the liquid, 10–35% from thermal expansivity of the host, and 5–40% from mass transfer between the inclusion and host. This complicates the application of simple element-partitioning schemes for back-calculating the effects of post-entrapment crystallization except in the simplest cases. We present a thermodynamic algorithm for PEC correction. This method is based on the self-consistent thermodynamic model set used in the MELTS software package. The algorithm moves backward through the PEC process, incrementally adding equilibrium crystal composition to the liquid while accounting for consequent variations in pressure and oxygen fugacity. Entrapment conditions are assumed to have been reached when the instantaneous liquidus solid composition most closely matches that of the bulk host crystal. Besides giving information on the degree of PEC and initial inclusion composition, the proposed algorithm can provide constraints on the pressure, temperature and oxygen fugacity at the time of entrapment. Olivine- and orthopyroxene-hosted inclusions from Popocatépetl, Mexico help constrain pre-eruption conditions for mixed magmas from recent eruptive products. Feldspar-hosted inclusions from Satsuma-Iwojima, Japan suggest that these magmas were substantially undersaturated with respect to supercritical vapor phase at the time of entrapment and underwent on the order of 29% post-entrapment crystallization. Quartz-hosted inclusions can potentially be employed in more silicic compositions, but this will require refinement of existing thermodynamic models.  相似文献   

人工神经网络在岩石变形温度估算中的应用     

李三忠  朱晓军 《岩石矿物学杂志》1995,(3)

Ｃｈｒｉｓｔｉｅ（１９６２）、Ｓｍｉｔｈ（１９７２）和张翊钧（１９８５）都提出了钠质斜长石的△１３１－（或σ）、Ａｎ与温度Ｔ的关系图，后来又提出了钠质斜长石变形温度的计算公式。但由于图解的不便之处及目前应用的公式中推断分界点的不确定性和σ、Ａｎ与Ｔ之间存在一种非线性关系的特点，本文基于具有高度非线性映射能力的人工神经网络，提出了求解岩石变形温度的新方法。文中先介绍了变形温度计的研究概况，然后阐述了ＡＮＮ（ＡｒｔｉｆｉｃｉａｌＮｅｕｒａｌＮｅｔｗｏｒ）模型，最后应用该模型估算岩石变形时的温度，经对比得出，利用人工神经网络在岩石变形温度估算中具有良好的应用效果。  相似文献   

桐庐、黄山花岗岩类岩体中碱性长石的出溶和超微双晶   总被引：1，自引：0，他引：1  

傅国飞  罗谷风 《矿物岩石》1990,(2)

本文研究了桐庐和黄山两地不同成因花岗岩类岩体中碱性长石的出溶和超微双晶。结果表明,碱性长石的出溶和超微双晶同岩体的成岩温度、冷却速率以及岩体成因类型和碱性长石的化学成份有关,成岩期后的热作用对碱性长石的出溶和超微双晶产生改造和破坏。  相似文献   

云南西盟小马撒喜山期花岗岩体的岩石学特征及岩石成因     

赵大贤 《岩石学报》1989,5(3)

云南省西部西盟小马撒花岗岩体出露于西盟隆起大黑山复背斜西翼,与上元古界西盟群变质岩呈侵入接触。黑云母Rb-Sr年龄为16.7Ma,Rb-Sr全岩等时线年龄为50.5Ma,属喜山期。熔融包体均—温度750—968℃,气液包体均—温度255—405℃。~(87)Sr/~(86)Sr初始比值为0.7121—0.7183、δ~(18)O值为 9.70— 10.24‰。小马撒花岗岩为陆壳部分熔融的花岗岩浆高侵位结晶的产物,属东南亚含锡S型花岗岩之北延部分。  相似文献   

黑龙江省科洛—二克山富钾火山岩的辉石和长石巨晶   总被引：3，自引：0，他引：3       下载免费PDF全文

邱家骧  刘蒙华 《地质科学》1989,(4):355-368

本文对富钾火山岩中单斜辉石、斜方辉石、长石巨晶的物理性质、化学成分、微量元素等特征进行了研究。文中还对巨晶的成因及对岩浆的影响问题,提出了作者自己的观点。  相似文献